Method and an apparatus for taking an undisturbed soil sample

ABSTRACT

A method and an apparatus for taking an undisturbed soil sample are described, by means of which the soil sample, which, during the introduction of a sampling tube into the soil, is surrounded by a hose, is supported substantially over its full length by means of a supporting tube which, after removing the sampling tube from the soil, is also used for transporting the sample to a laboratory. This supporting tube may consist of separate tube selections connected together by adhesive tape, so that the sample may be divided in easily transportable sections by cutting the adhesive tape and the sample. For facilitating the penetration of the sample into the sampling tube, a lubricating liquid may be used, and the sample may be supported near the lower end of the sampling tube by means of a supporting liquid, both liquids being immiscible. The lower part of the sampling tube is provided with means for pinching off the sample, and the corresponding secton of the supporting tube is weakened so that it may be deformed correspondingly, said pinching means being provided with means for locking it in its extreme positions, and with means for transferring pressing and pulling forces. Means are provided for closing the upper end of the hose and for guiding this end coaxially with the supporting tube for allowing the lubricating liquid to be uniformly distributed around the hose.

United States Patent Van De Beld et al.

1451 Sept. 12,1972

[54] METHOD AND AN APPARATUS FOR TAKING AN UNDISTURBED SOIL SAMPLE [72]Inventors: Roelof van de Beld; Heinrich K.S.P.

Begemann; Hendrikus J. Bos; Adriaan B. Mann, all of Laboratorium voorGrondmechanica, Stieltjesweg 2, Delft, Netherlands [22] Filed: Feb. 2,1970 [2i] Appl. No.: 7,789

[30] Foreign Application Priority Data Feb. 7, 1969 Netherlands..69020l9 [52] US. Cl. ..l7S/59, 175/245, 175/249 [51] Int. Cl. ..E2lb9/20, E2lb 25/00, E2lb 49/02 [58] Field of Search....l75/59, 60, 58,245, 246, 249,

Primary Examiner-Stephen J, Novosad AuomeyMarmorek & Bierman [5 7]ABSTRACT A method and an apparatus for taking an undisturbed soil sampleare described, by means of which the soil sample, which, during theintroduction of a sampling tube into the soil, is surrounded by a hose,is supported substantially over its full length by means of a supportingtube which, after removing the sampling tube from the soil, is also usedfor transporting the sample to a laboratory. This supporting tube mayconsist of separate tube selections connected together by adhesive tape,so that the sample may be divided in easily transportable sections bycutting the adhesive tape and the sample. For facilitating thepenetration of the sample into the sampling tube, a lubricating liquidmay be used, and the sample may be supported near the lower end of thesampling tube by means of a supporting liquid, both liquids beingimmiscible. The lower part of the sampling tube is provided with meansfor pinching off the sample, and the corresponding secton of thesupporting tube is weakened so that it may be deformed correspondingly,said pinching means being provided with means for locking it in itsextreme positions, and with means for transferring pressing and pullingforces. Means are provided for closing the upper end of the hose and forguiding this end coaxially with the supporting tube for allowing thelubricating liquid to be uniformly distributed around the hose.

29 Claims, 7 Drawing Figures PKTENTED 1972 i 3,690,389

SHEET 1 OF 3 INVENTORQ- 4404M mu BY flMJ- ATTORNEYS.

PATENTEBSEP 12 I972 SHEET 3 0F 3 INVENTORS: vM a 2M4,

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BY Alhq'mm WM )Zw M ATTORNEYI METHOD AND AN APPARATUS FOR TAKING ANUNDISTURBED SOIL SAMPLE This invention relates to a method and anapparatus for taking an undisturbed soil sample, which apparatuscomprises a cutting tube having a sharp cutting mouth, an annularchamber being disposed roundthe bottom end of the tube, in which chambertransversely resiliently stretchable hose may be arranged, which mayenter into the interior of the sampling tube through a slot near thecutting mouth and may be carried along with the penetrating sample, as aresult of which this sample is completely enclosed by the hose.Furthermore a supporting liquid may be used which may penetrate intothis chamber at least in the vicinity of the slot, for keeping the hosefree of the slot and for transversely supporting the sample at leastnear this slot.

Such a method and such an apparatus are described in the Dutch PatentNo. 125 036 and US. Patent No. 3,511,324. The latter Patent describes ahose provided with a liquidproof coating, in order to prevent that thesupporting liquid penetrates into the sample and that the water presentin the sample runs out. The supportin g liquid fills the small spacebetween the hose and the inner wall of the cutting tube and theextension tubes fixed thereto, as a result of which, on the one hand,the

friction between the hose and the tube is eliminated,

and, on the other hand, a lateral support of the sample is obtained bythe static pressure of the liquid, which lateral support is supplementedby the supporting force which is a result of the fact that the lateraldeformation of the hose is considerably reduced by the pulling forceexerted thereon in axial direction.

For obtaining an undisturbed drilling profile the latter method has beensatisfactory. However, in certain laboratory tests, an undisturbednessof the sample should be aimed at which cannot be achieved by the lattermethod. The support obtainable in this method may be insufficient insuch cases, since it is possible that the sample is either outwardlydeformed, at least locally, or is compressed by an excessive supportingpressure. In addition it is difficult to transfer the sample from thecutting tube into tubes suitable for the transport to the laboratorywithout additional deformation.

It is an object of the invention to improve these known methods andapparatus such that these disadvantages are eliminated.

For that purpose the method of I the invention is characterized in thata coaxial supporting tube is introduced into the cutting tube, whichcoaxial supporting tube extends up to the vicinity of the slot of thehose chamber and has an inner diameter which is only very little largerthan the outer diameter of the sample surrounded by the hose, alubricating liquid being introduced at the upper side of said supportingtube in order to fill the space between the hose and the supportingtube. Moreover, if necessary, a supporting liquid may be introduced intothe interspace between the supporting tube and the cutting tubecommunicating with the hose chamber.

The surface tension and the viscosity of the lubricating liquid and thewidth of the interspace between the supporting tube and the sample arechosen in such a manner that, as the sample enters the supporting tube,the lubricating liquid remains in said interspace, but a transverseinward deformation of the sample in consequence of the static pressureof said liquid or the expulsion of the liquid layer by the outwardpressure of the sample are avoided.

In particular the lubricating liquid has a greater cohesion to the wallof the supporting tube than to the wall of the hose, and, furthermore,the lubricating and supporting liquids may be mutually repellant inorder to prevent the supporting liquid from being carried along into thespace between the supporting tube and the sample.

By means of this method an unambiguous support of the sample is ensuredover its total length and independent of its composition, and, moreover,friction between the hose and the supporting tube is eliminated.

Preferably the supporting tube comprises individual tube sections,.thelength, of which corresponds to that of the cutting tube proper or toits extensions, said tube sections being placed together with theirterminal faces against each other and being connected to each other in asealed manner by means of an adhesive tape strip,

and, after withdrawal of the cutting tube from the soil, the individualtube sections together with the sample portions present therein areseparated from each other by cutting the adhesive tape strip, thehoseand the sample, and covering the cutting planes with a covering fortransporting the sample portions to the laboratory,

so that the disturbance of the sample when being transferred totransport tubes, such as required in the usual methods, is avoided.

In order to ensure a uniform penetration of the lubricating liquid intothe interspace between the sample and the supporting tube, and,especially, to prevent the hose and the supporting tube wall fromlocally contacting one another, an exactly axial guiding force may beexerted on the closed upper end of the hose.

The apparatus of the invention for carrying out this method ischaracterized by a separate rigid supporting tube which sealingly fitsinto a fitting provided in the cutting tube proper near the exit slotfor the hose and which is coaxially supported in the cutting tube.Particularly the interspace between the cutting tube and the supportingtube near the exit slot for the hose may be connected to the interior ofthe hose chamber.

In this manner it becomes possible that, as described in theafore-mentioned US. Pat. No. 3,511,324, that the hose will be pressedagainst the outer wall of the hose chamber near the lower side of thechamber by the supporting liquid present in the hose chamber, the latterbeing rounded towards the exit slot so that the hose emergesapproximately tangentially to the sample, and, at the same time, thesample is supported by the supporting liquid at the locationof said slotand prior to reaching the supporting tube. Since, furthermore, thesupport of the sample is entirely taken over by the supporting tube, thesupporting pressure exerted by the supporting liquid can be completelyadapted to the pressure value required near said slot. In the usualapparatus this is not possible since the supporting liquid should servefor the support of the entire sample.

Particularly, the inner tube which defines the hose chamber at the innerside may be provided at the inner side with longitudinal grooves, theintermediate ribs thereof contacting the supporting tube, said groovescommunicating, on the one side, with the interspace between thesupporting tube and the portion of the supporting tube proper and itsextensions above the hose chamber, and, on the other hand, with thelower side of the hose chamber. The passage through these grooves shouldbe sufficiently wide for ensuring sufficiently wide for ensuringsufficient supporting pressure at the lower side of the cutting tubewhere only the supporting liquid is active.

Particularly this inner tube may be a thin-walled tube abutting'againsta cage consisting of longitudinal thin rods which may contact thesupporting tube.

At their lower sides these rods may be mounted in a lower fitting ringdefining the exit slot for the hose, and their upper sides are mountedin an upper fitting ring defining the upper side of the hose chamber andbeing provided with recesses between the fixing points of the rods,saidrecesses communicating with the interspace between the cutting tubeand the supporting tube above this chamber, and the ring portionsbetween these recesses form guiding and supporting faces for thesupporting tube.

Particularly .the upper fitting ring for the rods is secured in thecutting tube by means of a ball joint, and the lower jetting ring isseparate from the cutting tube so that, as described in British Pat. No.1,129,130 the exit slot is prevented from being shut off at a possiblebending of the cutting tube.

, Furthermore the lower fitting ring is provided with an inner shoulderforming the fitting for the supporting tube.

The lower. edge of the lower fitting ring is outwardly and downwardlybevelled and forms, together with a ring which is'correspondinglybevelled at its outside and is secured in the cutting mouth portion ofthe cutting tube, the exit slot for the hose, the latter extendingsubstantially tangentially to the entering sample.

Thisufitting ring may, particularly, end in a thin resilient lip, andthe adjacent inner wall of the fitting ring extends substantiallyparallel to it, so that, when the cutting tube is upset when pressing itinto the soil, its slot width is not appreciably reduced.

In most cases the supporting tube consists of separate tube sections,the length of which being about the same as that of the extensions ofthe cutting tube, which tube sections can be placed together with theirterminal faces contacting each other, and the length of the lowermosttube sections fitting into the fitting at the lower end of the cuttingtube corresponding to the length of the cutting tubeproper.

Furthermore the apparatus of the invention is provided with a flexiblesleeve disposed above the hose chamber, said sleeve being fastened withboth ends in a ring, the lower end of which is unrotatably connected tothe lower cutting tube portion, and the upper end is coupled to acoupling tube which is rotatable but not slidable with respect to thecutting tube, which coupling tube may be firmly connected to the firstextension tube in order to be able to distort said flexible sleeve byrotation of said coupling tube and thereby pinching the sample disposedwithin said sleeve, said upper ring and coupling tube being providedwith locking means for maintaining said torsion sleeve in itw twistedposition. Similar parts are known, in respect of which reference is madeto the Dutch Pat. No. 125,036 mentioned before. For allowing the sampleto be pinched when using a supporting tube, the wall thickness of thelower tube section of the supporting tube which is placed into thecutting tube proper is reduced at the location of this torsion sleeve asfrom its outside such that the supporting tube can be pinched flat bymeans of said sleeve.

The coupling between said coupling tube and the lower cutting tubeportion comprises two grooves in the outer surface of the the couplingtube, which are symmetrically distributed over the surface and may havea length of arc of for example, which grooves are axially extended attheir ends, and the inner wall of the cutting tube is provided with lugsfitting into these grooves, all this in such a manner that in theirextreme positions the coupling tube and the cutting tube arenon-rotatably coupled to each other, but are axially movable withrespect to one another so that, in one extreme position, when this tubeis withdrawn, transverse stopping faces of the coupling tube and thecutting tube proper contact each other for transmitting the axiallydirected compressive and pulling forces respectively. The locking isreleased by moving the extension tubes axially in opposite senses,whereafter the other extreme position can be reached by rotation. Thus,at the end of the pressing action, the coupling tube is brought in itspulling position, in which, during rotation, the uppermost ring which iscoupled to this tube is carried along so that the torsion sleeve istwisted and is kept in the twisted position during pulling.

In large diameter samples an accordingly heavy pinching should occur forwhich purpose a relatively long torsion sleeve is required, which,however, leads to an excessive length of the portion in question of thecutting tube proper which may be weakened thereby. Nevertheless, forbeing able to use short torsion sleeve, its lower ring may benonrotatably but axially slidably coupled to the cutting tube by meansof a key, thus allowing the torsion sleeve to be shortened correspondingto its twisting as the upper ring is rotated. If desired, the lower ringmay be maintained in its lower position by means of a snap lock until,during twisting, a certain pulling force is exceeded.

Preferably the grooves in the cutting tube have such a helical shapethat the coupling tube in being rotated is displaced over a distancewhich is about equal but is opposite to the free travel of the couplingtube between its pressing and pulling positions. In this way a furtherdecrease in length may be obtained.

Furthermore the apparatus of the invention may be provided with a clampto be fixed to the upper end of the hose and provided with guiding lugswhich may bear against the inner wall of the supporting tube, in orderto ensure that the upper side of the hose remains as symmetrical aspossible with respect to the supporting tube, so that the lubricatingliquid may-uniformly penetrate into the interspace between the hose andthe supporting tube, the interspace between the lugs being sufficientlylarge for allowing an undisturbed passage of the lubricating liquid.

Particularly, said clamp comprises a circular disc which may be clamped,with interposition of the free rim of the hose, on a plug disposedwithin the hose, this plate being provided with guiding lugs. Morespecifically these lugs may be spaced from said clamping plate by meansof substantially axial connecting pieces in order to interfere as littleas possible the lubricating liquid from forming a film.

For further decreasing the risk of tilting of the clamp, a pin may bedisposed in the center of and perpendicularly to the clamping plate, towhich pin the drawing string may be fastened, this pin, near its freeend, being provided with a number of guiding lugs bearing against thewall of the supporting tube.

The invention will be explained below with reference to the drawing, inwhich:

FIG. lshows a longitudinal section of a cutting tube according to theinvention provided with cutting mouth, without the protective hose andthe supporting tube;

FIG. 2 shows a section on the line Il-II of FIG. 1;

FIG. 3 shows a view, partially in section, of the inner tube of thiscutting tube with a supporting tube disposed therein;

FIG. 4 shows a section on the line IV-IV of FIG. 3;

FIG. 5 shows a section through the lower part of the cutting tube with asupporting tube placed therein during the penetration of a soil sample,as well as means for closing and guiding the end of the hose filled withthe sample; and

FIGS. 6A and 6B show schematic developments of guiding grooves of acoupling part of the cutting tube. FIG. I shows a cutting tube 1 properprovided at one end, in the usual way, with a cutting mouth 2, whichtube may be extended at its other end by means of extension tubes 3.Within the lower portion of this cutting tube an annular hose chamber 4is closed at its upper side, and ends at its lower end into a slot 6extending substantially tangent to the inner wall 7 of the cutting mouth2. The end wall 8 of this chamber is rounded so that the hose present inthe chamber 4 can be lead out tangentially to the sample, as shown inFIG. 5. This construction is of current design.

The inner tube 5, however, differs from the usual inner tube. This tubecomprises an upper fitting ring 9 provided at its upper end with a moreor less spherical thickening 10 which fits into corresponding seat 11 ofthe outer tube 1 so that the fitting 9 is adjustably held in the outertube. Furthermore the inner tube 5 comprises a lower fitting ring 12,the bevelled inner wall 13 of which defining the exit slot 6. Bothfitting rings are connected to each other by a number of thin rods 14made of stainless steel or the like. These rods 14 are fixed in lugs 15which, as shown in FIG. 2, extend into the bore of the fitting ring 9 atthe latters lower side, and are separated from each other by recesses16. In addition a thin-walled tube 17 of stainless steel or the like isdisposed round the cage formed by these rods (FIGS. 3 and 4), said tubeforming the inner wall of the hose chamber 4. In this way the lowerfitting ring 12 is suspended from the adjustable upper fitting ring 9,so that, from the occurrence of minor distortions of tube 1, the slot 6is kept substantially symmetrically, in order to avoid the risk of thehose being pinched, as described in British Pat. No. 129,130.

Both fitting rings 9 and 12, together with the cage 14, form a supportfor a removable supporting tube 18 (FIGS. 3 and 4). This tube 18 has aclose fit in a seat 19 of the fitting ring 12. The inner diameter oftube 18 and that of the portion 20 of the fitting ring 12 contiguous tothe seat 19 are approximately equal to the inner diameter of the end 7of the cutting mouth so that, as appears from FIG. 5, the samplesurrounded by a hose slidingly fits into the tube 18 and is laterallysupported thereby.

The lugs 15 in the upper fitting ring 9 have an interior circular innerwall, the diameter of which corresponds to the outer diameter of thesupporting tube 18. Also at its upper end the fitting ring 9 is providedwith interior lugs 21, the inner faces of which rest against the tube18, with passages 22 lying between these lugs. The extension tubes 3 maybe provided with such lugs too in order to maintain the supporting tube18 co-axially and at a small distance from the inner wall of thesetubes.

When using such a sampler, the cutting tube 1 is pressed into the soilin the usual way and is provided with extension tubes 3. The'supportingtube 18 comprises individual sections having a length approximatelyequal to that of the extension tubes. These tube sections are placedtogether with their terminal faces against each other, and are connectedto each other by means of adhesive tape. The lower supporting tubewhich, as will be described below, slightly differs from the other tubesections, is inserted into the seat 19 of the fitting ring 12 and will,then, be supported by the lugs 15 and 21, as clearly appears from FIG.3. A supporting liquid is poured into the interspace between the tubesections 18 and the extension tubes 3, which liquid will flow downwardsthrough the recesses 22 and 16 through the interspaces between the rods14. The inner sides of these rods rest against the supporting tube 18(FIG. 4) and uniformly support this tube against the radial forcesexercised by the sample. At its lower end the tube 17 is provided with anumber of holes 23 which open into the hose chamber 4. Thus thesupporting liquid can penetrate into the hose chamber 4.

As appears from FIG. 5, the supporting liquid will press the hose 24 inthe chamber 4 and near the holes 23 outwardly. Since the hose is pleatedaround the tube 17 in the chamber 4, the supporting liquid cannotpenetrate very much into this chamber. However, these pleats arefastened when pulling the hose through the slot 6. The hose is pressedby the supporting liquid against the rounding 8 so that the hose leavesthe slot 6 substantially tangentially to the sample 25. The staticpressure of the liquid in the complete cutting tube acts upon theexterior of the hose and the slot, so that, during its penetration fromthe cutting mouth wall 7 to the inner wall of the supporting tube 18,the sample is transversely supported at the location of the mouth of theslot. Since, as will be described below, this supporting liquid needsonly be active at the location of the slot 6, its composition may bechosen so that its pressure in that point is just sufficient forsupporting the sample against lateral deformation. In the known methodsfor taking samples with such a hose the supporting liquid has, inaddition, to provide for an additional supporting pressure over the fulllength of the sample, so that, when the samples consist of layers havinga considerably different compressibility, there is always the risk ofthe supporting pressure being locally too high or too low. According tothe invention, however, the sample is completely supported by thesupporting tube 18 so that this risk is avoided and the support suppliedby the supporting liquid may be exclusively adjusted to the slot region.

As a result of the radial pressure of the sample 25, the hose 24 ispressed against the inner wall of the tube 18, thus producing aconsiderable friction which will induce deformation of the sample. Foreliminating this friction a lubricating liquid is injected into the tube18 having such a viscosity, surface tension and other physicalproperties that it forms a thin film between the supporting tube 18 andthe hose 24. The adhesion of said liquid to the tube 18 should begreater than to the hose 24 in order to prevent the liquid from beingcarried along as the sample penetrates. The coherence and thickness ofthe layer should be sufficient for preventing that the layer is pressedaway as a result of a local radial pressure, and that the hose contactsthe tube wall. On the other hand this layer may not be so thick that thestatic pressure of the column of liquid will act upon the hose. Finallythis lubricating liquid should be immiscible with the supporting liquidused, in order to avoid that the supporting liquid is carried along withthe hose.

As usual the supporting liquid may be an aqueous suspension, thespecific weight of which is adapted to the soil pressure to becounteracted. The lubricating liquid may be a lubricating oil type ofliquid in which if necessary additional substances have been dissolvedor suspended for adjusting the specific weight. As a matter of fact manyother pairs of liquids may be used meeting the requirements.

For ensuring a uniform lubricating layer to be formed, a care should betaken that the upper side of the hose, which is closed and connected toa string which, during the introduction of the cutting tube into thesoil, is kept tensioned for maintaining the upper end of the hose at afixed height (showing that the sampling properly proceeds), be keptexactly coaxially in order to delimit, with the supporting tube 18, aslot opening which is as uniform as possible. For that purpose a clampshown in FIG. is used. This clamp substantially comprises a plug 26 anda disc 27. Before the sample cutting is started, the disc 27 isintroduced into the inner tube, and then the hose 24 which has beenpulled inwards through the slot 6 is folded between the disc 27 and theplug 26, which plug is subsequently connected to the disc 27 by means ofa screw connection so that the hose is clamped between the plug and thedisc. The disc 27 is provided with a plurality of lugs which areuniformly distributed over the circumference, the outer diameter ofwhich lug assembly being equal to the inner diameter of the tube 18, sothat the disc is accurately centered in the tube 18. The diameter of thedisc 27 between the lugs 28 is smaller so that the lubricating liquidmay enter the interspace 29 between the hose and the tube 18. Preferablythe lugs are slightly offset with respect to the plane of the disc 27 asshown in F IG. 5.

As shown the disc 27 is connected to a rod 30 which,

at its free end, is provided with an eye 31 to which the pulling string32 referred to may be connected. In order to avoid tilting of the clampassembly which would lead to the slot 29 being closed off, it isadvisable to provide a number of radial arms 33 in the vicinity of theeye 31 and the ends of these arms may be provided with lugs abuttingagainst the inner wall of the tube 18.

In withdrawing the cutting tube from the soil, it should be avoided thatthe sample sags as soon as the soil pressure disappears. For thatpurpose it is custom ary to pinch off the sample near the cutting mouth.Generally a resilient sleeve is used to that end, one end of which beingfixed to the first extension tube, and the other end being coupled tothe first extension tube, both tube portions being rotatably connectedto each other. When the last extension tube protruding from the soil isrotated, the first extension tube will rotate with respect to thecutting tube proper, in consequence of which said sleeve is twisted andthe sample is constricted, so that a support for the sample is provided.Without additional provisions, however, the presence of the supportingtube 18 according to the invention will make it impossible to constrictthe sample.

In FIG. 1 such a pinching assembly isshown. At the location of thisassembly, the wall thickness of the supporting tube 18 has been reduced,e.g. by turning off the outside of the wall in said region, as indicatedat 34. This renders the wall sufficiently yieldable for beingconstricted when being pinched. Thereby its radial stiffness decreases,but by the presence of the supporting liquid which is also present roundthe pinching assembly sufficient lateral support is ensured.

In a cutting tube destined for large diameter samples the pinchingassembly has to be slightly altered. The assembly shown in FIG. 1comprises the usual torsion sleeve 35 which is clamped between twofitting rings 36 and 37. The upper fitting ring abuts against a shoulder38 of the outer tube 1 and is coupled to a coupling tube 40 by means ofone or more teeth 39, which coupling tube rotatably fits in the end oftube 1 and may be connected to the first extension tube 3. This couplingtube 40 is provided with two circumferential grooves 41 each spanning anarc of about lugs 42 provided at the inside of the tube 1 engaging thesegrooves. The ends 43 and 44 are axially extended and thus form lockingseats for the lugs 42 as shown in FIG. 6.

When the tubes are pressed down, each lug 42 is in the correspondingseat 43. In this position the sleeve 35 is untensioned, and the end face45 of the coupling tube 40 may contact the fitting ring 37 as aconsequenceof the axial extrusion of the end 43 of the groove, so thatthe pressing force exerted by the extension tubes on the coupling tubemay be transmitted to the outer tube 1 via the shoulder 38. Thissituation is schematically shown in FIG. 6A in continuous lines. In thissituation the lugs 42 are secured against rotation in the groove ends43.

When the cutting tube has to be withdrawn from the soil, a pulling forceis exerted on the extension tubes causing the lugs 42 to be releasedfrom the groove ends 43. Thereafter the extension tubes are rotated, sothat each lug 42 passes through the corresponding groove 41 until theother end 44 is reached. When, subsequently, the extension tubes arepulled again, the lugs 42 will snap into the axial extensions 44 of thegrooves 41. This causes a shoulder face 46 opposed from the end face 45to contact a shoulder 47 of the outer tube 1, so that the pulling forceexerted on the coupling tube 40 is transmitted in turn to the outer tube1.

During rotation of the coupling tube 40 with respect to the outer tube1, the fitting ring 37 is engaged by the teeth 39. Theother fitting ring36 is not rotatable with respect to the outer tube 1 so that the torsionsleeve 35 disposed between both rings is twisted. In reaching its finalposition the coupling tube 40 is secured in the groove ends 44 by thelugs 42, so that the torsion sleeve 35 is held in its twisted position.

When the sample has a large diameter, the torsion sleeve should besubmitted to a considerable constriction. In order to restrict thelength of the twisting assembly and, thereby, to avoid any undesiredweakening of the cutting tube proper, the fitting ring 36 is, as shown,coupled axially slidably but non-rotatably to the tube 1, in order toallow for the decrease in length to which a short torsion sleeve issubmitted when being twisted. Preferably the ring 36 is held in itsextreme position by means of a snap lock 48 which snap lock will yieldto a given pulling force.

In order to enable a further decrease in length of the cutting tubeproper, which is favorable with a view to the stroke of the press usedfor pressing the sampler into the soil, the grooves 41 may have ahelical outline as'shown in FIG. 6B. The pitch of these grooves shouldbe such that the displacement necessary for releasing a lug 42 from agroove end is recovered in rotating the coupling tube, so that the freetravel between pulling and pushing may be reduced by about onehalf.

When the sampler is withdrawn from the soil, the extension tubes 3 aresuccessively unscrewed. Then, at the same time, the correspondingsections of the supporting tube 18 are separated from one another bycutting both the strip of adhesive tape connecting two tube sections andthe sample inside the tube with the aid of a knife, whereafter thesample is covered with a plate. Then the sample can be transported inthe tube section. The cutting can also be done with a cutting platewhich, at the same time, serves as a cover plate. The cutting can alsobe done with the aid of a cutting thread which is connected to anelectric direct current source for locally increasing the water pressureduring the cutting as a result of the voltage difference, and, thereby,decreasing the intergranular pressure, causing the friction ot thecutting thread to be reduced.

Particularly the lower fitting ring 12 may end into a thin elastic lipwhich, together with another substantially parallel lip in alignmentwith the inner wall 7, defines a slot, so that, when the outer tube 1 isupset during pressing, the width of the slot is not appreciably reduced,in order to avoid clamping of the hose.

Instead of the cage consisting of rods 14 and a surrounding tube 17, atube provided with inwardly directed longitudinalribs may be used, whichribs serve the same purpose as the rods.

Within the scope of the invention many variations are still possible.

We claim:

1. A method for taking an undisturbed soil sample with the aid of acutting tube with a sharp cutting mouth, an annular chamber beingdisposed round the bottom end of this tube, in which chamber atransversely stretchable hose may be arranged which may enter into theinterior of the sampling tube through a slot near the cutting mouth, andmay be carried along with the penetrating sample, as a result of whichthis sample is completely enclosed by the hose, characterized by thesteps of introducing a coaxial supporting tube into the cutting tube,which coaxial supporting tube extends down to the vicinity of the slotof the hose chamber, the inner diameter of this tube being only slightlylarger than the outer diameter of the sample surrounded by the hose, andintroducing a lubricating fluid at the upper end of said supporting tubein order to fill the space between the hose and the supporting tube.

2. The method according to claim 1, wherein a sup porting liquid isintroduced into the hose chamber at least in the vicinity of its exitslot for keeping the hose free of the slot and transversely supportingthe sample at least in the vicinity of said slot, characterized in thatthe supporting liquid is poured into the interspace between thesupporting tube and the cutting tube, the latter communicating with thehose chamber.

3. The method according to claim 2, characterized in that thelubricating liquid is immiscible with the supporting liquid in order toavoid that the supporting liquid be carried along with the hose. 4. Themethod according to claim 1, characterized in that the surface tensionand the viscosity of the lubricating liquid and the width of theinterspace between the supporting tube and the sample are such that, asthe sample penetrates into the supporting tube, the lubricating liquidremains in said interspace, but a transverse inward deformation of thesample in consequence of the static pressure of said liquid and theexpulsion of the liquid layer by the outward pressure of the sample isavoided.

5. The method according to claim 1, characterized in that thelubricating liquid has a greater adhesion to the wall of the supportingtube than to the wall of the hose.

6. The method according to claim 1 characterized by the steps ofextending, during the cutting, the supporting tube by supportingextension tubes disposed within the cutting tube proper, the length ofsaid supporting extension tubes corresponding to that of the extensiontubes of the cutting tube proper, said supporting extension tubes beingplaced with their terminal faces abutting each other and being connectedto each other in a sealed manner by means of an adhesive tape, and afterwithdrawal of the cutting tube from the soil and the subsequentloosening of the extensions of the cutting tube, separating theindividual supporting extension tubes from each other by cutting theadhesive tape and the sample, and covering the cutting planes withcovering plates.

7. The method according to claim 6, characterized by cutting theadhesive tape with the aid of a covering plate having a sharp edge.

8. The method according to claim 6, characterized in that the sample istransported within the supporting tubeand supporting extension tubes.

9. The apparatus for taking an undisturbed soil sample, comprising acutting tube having a cutting mouth, an annular chamber disposed roundthe interior of the lower end of said cutting tube, into which a hosecan be inserted, a sample tube arranged within said cutting tube, saidannular chamber communicating with the interior of the sample tube bymeans of a circular slot disposed in the vicinity of said cutting mouth,fitting means disposed in the vicinity of said circular slot, and adetachable rigid supporting tube sealingly fitting into said fittingmeans, and being coaxially supported in said cutting tube, said sampletube defining said hose chamber and is provided at the inside withlongitudinal grooves, the ribs between said grooves contacting saidsupporting tube, said grooves connecting the lower end of said hosechamber with the interspace between the supporting tube and the portionabove the hose chamber of the cutting tube proper and its extensions.

10. The apparatus according to claim 9, characterized in that the sampletube includes a thin-walled inner tube disposed round a cage consistingof longitudinal rods which contact said inner tube and the supportingtube.

11. The apparatus according to claim 10, characterized in that, at theirlower ends, the rods of the cage are mounted in a lower fitting ringsupported in the circular slot of the hose chamber and, at their upperends, are mounted in an upper fitting ring supported in the inner wallof said cutting tube above said hose chamber, said fitting rings beingprovided with recesses between the fixing points of the rods, whichrecesses communicate with the interspace between the cutting tube andthe supporting tube above said chamber, the ring portions between theserecesses forming guiding and supporting faces for the supporting tube.

12. The apparatus according to claim 11, characterized in that the upperfitting ring is secured in the cutting tube by means of a ball joint,the lower fitting ring being separate from the cutting tube and beingsupported by the rods only.

13. The apparatus according to claim 12, characterized in that the lowerfitting ring is provided with an inner shoulder forming the fitting forthe supporting tube, the diameter of the opening in this fitting meansring below said shoulder being at least about equal to the innerdiameter of the supporting tube.

14. The apparatus according to claim 12, characterized in that the loweredge of the lower fitting ring is widened outwardly and downwardly,defining, together with a ring which is correspondingly bevelled at itsinside and is secured in the cutting mouth portion of the cutting tube,the circular slot of the hose chamber, the latter extendingsubstantially tangentially to the entering sample.

15. The apparatus according to claim 18, characterized in that thefitting ring ends in a resilient lip, and in that the adjacent innerwall of the lower fitting ring extends substantially parallel to it.

16. The apparatus according to claim 9, characterized in that thesupporting tube consists of separate tube sections, the length of whichbeing about the same as that of the extension tubes of the cutting tubeproper, which tubes sections may be placed together with their terminalfaces against each other, the lower tube section fitting into thefitting at the lower end of the cutting tube having a lengthcorresponding to the length of the cutting tube proper.

17. The apparatus according to claim 16, characterized by coveringplates for the tube sections of the supporting tube by which the samplepieces present in these tube sections can be covered at the location ofthe connection between two tube sections after the sample has been cutthrough.

18. The apparatus according to claim 9, provided with a flexible sleevedisposed above the hose chamber, said sleeve being fastened with bothends in a ring, the lower end of which being unrotatably connected tothe lower cutting tube portion, and the upper end being coupled to acoupling tube which is rotatable but not slidable with respect to thecutting tube, which coupling tube may be firmly connected to the firstextension tube in order to twist said flexible sleeve by rotation ofsaid coupling tube and thereby pinching the sample disposed within saidsleeve, said upper ring and coupling tube being provided with lockingmeans for maintaining said torsion sleeve in its twisted position,characterized in that at the location of the torsion sleeve thesupporting tube possesses a wall portion, the thickness of which isreduced from the outside in order to make the supporting wall yieldablein that region so that it can be pinched flat by the torsion sleeve.

19. The apparatus according to claim 18, characterized in that thecoupling between the coupling tube and the lower cutting tube comprisestwo grooves in the outer surface of the coupling tube, which aresymmetrically distributed over the surface, and have an arc length ofabout which grooves are axially extended at their ends, the inner wallof the cutting tube being provided with two lugs fitting into acorresponding groove, all this in such a manner that in their extremepositions the coupling tube and the cutting tube arenon-rotatablycoupled to each other, but are axially movable with respect to oneanother, so that, in one extreme position, when the cutting tube ispressed into the soil, and in the other position, when this tube iswithdrawn, transverse stopping faces of the coupling tube and thecutting tube proper are capable of contacting each other fortransmitting the compressive and pulling forces respectively.

20. The apparatus according to claim 19, characterized in that thegrooves in the cutting tube have such a helical shape, that the couplingtube in being rotated is axially displaced over a distance which isabout equal but is opposite to the free travel of the coupling tubebetween its pressing and pulling positions.

21. The apparatus according to claim 18, characterized in that the lowerring of the torsion sleeve is non-rotatably but axially movably coupledto the cutting tube by means of a longitudinal key.

22. The apparatus according to claim 21, characterized in that the lowerring of the torsion tube canbe maintained in its lower position by meansof a snap lock, until, during twisting of the sleeve, a certain pullingforce has been exceeded.

23. The apparatus according to claim 9, characterized by a clamp forclosing the upper end of the hose and provided with guiding lugs whichare connected to the clamp and which abut the inner wall of thesupporting tube so that the upper side of the hose is held substantiallysymmetrically with respect to the wall of the supporting tube.

24. The apparatus according to claim 23, characterized in that the clampcomprises a circular clamping plate provided with lugs, which plate,while interposing the free edge of the hose, may be clamped on a closingplug disposed within the hose.

25. The apparatus according to claim 24, characterized in that theguiding lugs are spaced from the 28. An apparatus for taking anundisturbed soil sample, comprising a cutting tube operable for beingpressed into the soil without rotation from the soil surface and havinga cutting mouth at the lower end thereof, coaxial extension tubesremovably connectable to the upper end of said cutting tube andextending uninterruptedly to the soil surface, the bore of saidextension tubes being substantially equal to the bore of said cuttingmouth and thereby to the diameter of the sample to be taken, an annularrecess provided in the inner wall of said cutting tube in the vicinityof said cutting mouth, said annular recess being terminated at its lowerend with a rounded annular groove, a coaxial inner tube disposed withinsaid cutting tube so as to define with said annular recess an annularchamber for a hose communicating with the interior of said inner tube bya circular slot resulting between the lower end of said inner tube andsaid annular groove, a removable, rigid, sample support tube insertableinto said inner tube, fitting means provided on said inner tube forsealingly supporting said sample support tube near said slot and foraxially spacing said sample support tube from said inner tube, the innerdiameter of said sample support tube being substantially equal to thebore of said cutting mouth and being in alignment therewith, wherebysaid extension tubes are usable as a transport container for the samplecut by said cutting mouth and surrounded by said hose drawn from saidannular chamber through said slot.

29. An apparatus according to claim 28 further comprising piercing meanswithin said cutting tube, said extension tubes being rotatably connectedto said cutting tube and operable for actuating said piercing meanswhile said cutting tube is stationary due to the friction cause by thesurrounding soil.

1. A method for taking an undisturbed soil sample with the aid of acutting tube with a sharp cutting mouth, an annular chamber beingdisposed round the bottom end of this tube, in which chamber atransversely stretchable hose may be arranged which may enter into theinterior of the sampling tube through a slot near the cutting mouth, andmay be carried along with the penetrating sample, as a result of whichthis sample is completely enclosed by the hose, characterized by thesteps of introducing a coaxial supporting tube into the cutting tube,which coaxial supporting tube extends down to the vicinity of the slotof the hose chamber, the inner diameter of this tube being only slightlylarger than the outer diameter of the sample surrounded by the hose, andintroducing a lubricating fluid at the upper end of said supporting tubein order to fill the space between the hose and the supporting tube. 2.The method according to claim 1, wherein a supporting liquid isintroduced into the hose chamber at least in the vicinity of its exitslot for keeping the hose free of the slot and transversely supportingthe sample at least in the vicinity of said slot, characterized in thatthe supporting liquid is poured into the interspace between thesupporting tube and the cutting tube, the latter communicating with thehose chamber.
 3. The method according to claim 2, characterized in thatthe lubricating liquid is immiscible with the supporting liquid in orderto avoid that the supporting liquid be carried along with the hose. 4.The method according to claim 1, characterized in that the surfacetension and the viscosity of the lubricating liquid and the width of theinterspace between the supporting tube and the sample are such that, asthe sample penetrates into the supporting tube, the lubricating liquidremains in said interspace, but a transverse inward deformation of thesample in consequence of the static pressure of said liquid and theexpulsion of the liquid layer by the outward pressure of the sample isavoided.
 5. The method according to claim 1, characterized in that thelubricating liquid has a greater adhesion to the wall of the supportingtube than to the wall of the hose.
 6. The method according to claim 1characterized by the steps of extending, during the cutting, thesupporting tube by supporting extension tubes disposed within thecutting tube proper, the length of said supporting extension tubescorresponding to that of the extension tubes of the cutting tube proper,said supporting extension tubes being placed with their terminal facesabutting each other and being connected to each other in a sealed mannerby means of an adhesive tape, and after withdrawal of the cutting tubefrom the soil and the subsequent loosening of the extensions of thecutting tube, separating the individual supporting extension tubes fromeach other by cutting the adhesive tape and the sample, and covering thecutting planes with covering plates.
 7. The method according to claim 6,characterized by cutting the adhesive tape with the aid of a coveringplate having a sharp edge.
 8. The method according to claim 6,characterized in that the sample is transported within the supportingtube and supporting extension tubes.
 9. The apparatus for taking anundisturbed soil sample, comprising a cutting tube Having a cuttingmouth, an annular chamber disposed round the interior of the lower endof said cutting tube, into which a hose can be inserted, a sample tubearranged within said cutting tube, said annular chamber communicatingwith the interior of the sample tube by means of a circular slotdisposed in the vicinity of said cutting mouth, fitting means disposedin the vicinity of said circular slot, and a detachable rigid supportingtube sealingly fitting into said fitting means, and being coaxiallysupported in said cutting tube, said sample tube defining said hosechamber and is provided at the inside with longitudinal grooves, theribs between said grooves contacting said supporting tube, said groovesconnecting the lower end of said hose chamber with the interspacebetween the supporting tube and the portion above the hose chamber ofthe cutting tube proper and its extensions.
 10. The apparatus accordingto claim 9, characterized in that the sample tube includes a thin-walledinner tube disposed round a cage consisting of longitudinal rods whichcontact said inner tube and the supporting tube.
 11. The apparatusaccording to claim 10, characterized in that, at their lower ends, therods of the cage are mounted in a lower fitting ring supported in thecircular slot of the hose chamber and, at their upper ends, are mountedin an upper fitting ring supported in the inner wall of said cuttingtube above said hose chamber, said fitting rings being provided withrecesses between the fixing points of the rods, which recessescommunicate with the interspace between the cutting tube and thesupporting tube above said chamber, the ring portions between theserecesses forming guiding and supporting faces for the supporting tube.12. The apparatus according to claim 11, characterized in that the upperfitting ring is secured in the cutting tube by means of a ball joint,the lower fitting ring being separate from the cutting tube and beingsupported by the rods only.
 13. The apparatus according to claim 12,characterized in that the lower fitting ring is provided with an innershoulder forming the fitting for the supporting tube, the diameter ofthe opening in this fitting means ring below said shoulder being atleast about equal to the inner diameter of the supporting tube.
 14. Theapparatus according to claim 12, characterized in that the lower edge ofthe lower fitting ring is widened outwardly and downwardly, defining,together with a ring which is correspondingly bevelled at its inside andis secured in the cutting mouth portion of the cutting tube, thecircular slot of the hose chamber, the latter extending substantiallytangentially to the entering sample.
 15. The apparatus according toclaim 18, characterized in that the fitting ring ends in a resilientlip, and in that the adjacent inner wall of the lower fitting ringextends substantially parallel to it.
 16. The apparatus according toclaim 9, characterized in that the supporting tube consists of separatetube sections, the length of which being about the same as that of theextension tubes of the cutting tube proper, which tubes sections may beplaced together with their terminal faces against each other, the lowertube section fitting into the fitting at the lower end of the cuttingtube having a length corresponding to the length of the cutting tubeproper.
 17. The apparatus according to claim 16, characterized bycovering plates for the tube sections of the supporting tube by whichthe sample pieces present in these tube sections can be covered at thelocation of the connection between two tube sections after the samplehas been cut through.
 18. The apparatus according to claim 9, providedwith a flexible sleeve disposed above the hose chamber, said sleevebeing fastened with both ends in a ring, the lower end of which beingunrotatably connected to the lower cutting tube portion, and the upperend being coupled to a coupling tube which is rotatable but not slidablewith respect to the cutting tube, which coupling tube may be firmlyconnected to the first extension tube in order to twist said flexiblesleeve by rotation of said coupling tube and thereby pinching the sampledisposed within said sleeve, said upper ring and coupling tube beingprovided with locking means for maintaining said torsion sleeve in itstwisted position, characterized in that at the location of the torsionsleeve the supporting tube possesses a wall portion, the thickness ofwhich is reduced from the outside in order to make the supporting wallyieldable in that region so that it can be pinched flat by the torsionsleeve.
 19. The apparatus according to claim 18, characterized in thatthe coupling between the coupling tube and the lower cutting tubecomprises two grooves in the outer surface of the coupling tube, whichare symmetrically distributed over the surface, and have an arc lengthof about 170*, which grooves are axially extended at their ends, theinner wall of the cutting tube being provided with two lugs fitting intoa corresponding groove, all this in such a manner that in their extremepositions the coupling tube and the cutting tube are non-rotatablycoupled to each other, but are axially movable with respect to oneanother, so that, in one extreme position, when the cutting tube ispressed into the soil, and in the other position, when this tube iswithdrawn, transverse stopping faces of the coupling tube and thecutting tube proper are capable of contacting each other fortransmitting the compressive and pulling forces respectively.
 20. Theapparatus according to claim 19, characterized in that the grooves inthe cutting tube have such a helical shape, that the coupling tube inbeing rotated is axially displaced over a distance which is about equalbut is opposite to the free travel of the coupling tube between itspressing and pulling positions.
 21. The apparatus according to claim 18,characterized in that the lower ring of the torsion sleeve isnon-rotatably but axially movably coupled to the cutting tube by meansof a longitudinal key.
 22. The apparatus according to claim 21,characterized in that the lower ring of the torsion tube can bemaintained in its lower position by means of a snap lock, until, duringtwisting of the sleeve, a certain pulling force has been exceeded. 23.The apparatus according to claim 9, characterized by a clamp for closingthe upper end of the hose and provided with guiding lugs which areconnected to the clamp and which abut the inner wall of the supportingtube so that the upper side of the hose is held substantiallysymmetrically with respect to the wall of the supporting tube.
 24. Theapparatus according to claim 23, characterized in that the clampcomprises a circular clamping plate provided with lugs, which plate,while interposing the free edge of the hose, may be clamped on a closingplug disposed within the hose.
 25. The apparatus according to claim 24,characterized in that the guiding lugs are spaced from the clampingplate by means of axially extending connecting pieces.
 26. The apparatusaccording to claim 24, characterized in that in the center of theclamping plate and vertically directed thereto a pin is disposed, towhich a pulling string can be fixed for guiding the upper end of thesample.
 27. The apparatus according to claim 26, characterized in thatin the vicinity of its free end the pin is provided with a number ofsymmetrical guiding lugs abutting the inner wall of the supporting tube.28. An apparatus for taking an undisturbed soil sample, comprising acutting tube operable for being pressed into the soil without rotationfrom the soil surface and having a cutting mouth at the lower endthereof, coaxial extension tubes removably connectable to the upper endof said cutting tube and extending uninterruptedly to the soil surface,the bore of said extension tubes being substantially equal to the boreof said cutting mouth and thereby to the diameter of the sample to betaken, an annular recEss provided in the inner wall of said cutting tubein the vicinity of said cutting mouth, said annular recess beingterminated at its lower end with a rounded annular groove, a coaxialinner tube disposed within said cutting tube so as to define with saidannular recess an annular chamber for a hose communicating with theinterior of said inner tube by a circular slot resulting between thelower end of said inner tube and said annular groove, a removable,rigid, sample support tube insertable into said inner tube, fittingmeans provided on said inner tube for sealingly supporting said samplesupport tube near said slot and for axially spacing said sample supporttube from said inner tube, the inner diameter of said sample supporttube being substantially equal to the bore of said cutting mouth andbeing in alignment therewith, whereby said extension tubes are usable asa transport container for the sample cut by said cutting mouth andsurrounded by said hose drawn from said annular chamber through saidslot.
 29. An apparatus according to claim 28 further comprising piercingmeans within said cutting tube, said extension tubes being rotatablyconnected to said cutting tube and operable for actuating said piercingmeans while said cutting tube is stationary due to the friction cause bythe surrounding soil.